The present invention provides for an apparatus and/or method of measuring the height of a tread element such as a lug, a traction element or a rib of a tire. More specifically, this invention relates to the measuring of the lugs, traction elements or ribs of large tires such as those commonly known as "off-the-road tires" and "agricultural tires".
An ideal tire under ideal conditions would be expected to wear uniformly. For example, after so many miles "X", the tire tread would be expected to wear a certain amount "Y" uniformly across the entire tread surface until the entire surface was worn completely out at the same time. However, this rarely, if ever, happens in the real world. Parts of the tread of a tire may wear more rapidly than other parts due to a number of different known factors such as alignments, over/under inflation, type of operation, the surface they are operated on, etc. This may even be more pronounced with the tread elements for "off-the-road tires" or "agricultural" tires. Generally, as compared to passenger tires, these tires have larger and wider tread elements, lugs, etc., separated by larger and wider grooves. Because of the large tread elements, there is more surface area which may allow for different parts of the same tread element to wear differently. That is, different parts of the tread elements (lugs, etc.) may have different amounts of tread remaining. Prior art measuring gauges have not allowed a person in the field to measure a particular point on a tread element. As a result, these devices may not be accurately measuring that particular lug and/or the remaining tread of the tire. It is important to accurately measure the remaining tread on a tire for both tire testing data and to assure an accurate adjustment or prorated amount on a refund or credit to a customer for the unused portion of the tread.
Generally, the prior art measuring gauges span two adjacent lugs and measure down from there to the bottom of the groove. These devices use the top of the tread elements as the reference point. Therefore, these devices are actually measuring the depth of the grooves.
One such prior art device is disclosed in U.S. Pat. No. 3,269,019 to H W Krohn for a "Tread Depth Gauge". This device has a member which extends across the outer surface of one lug to the outer surface of another lug. A plunger moves down to engage the bottom of the groove. The distance traveled by the plunger corresponds to the depth of the groove. This type of device may not always give the true height of the lug due to the imperfections or the uneven wear of the outer surface on large lugs such as those found on "off-the-road" and "agricultural" tires.
While this invention is related especially for use with "off-the-road" and "agricultural" tires, it is noted that this device and/or method can also be used with other tires such as passenger tires, truck tires, terra tires, etc.